四川省年昼雨的空间变化特征

Spatial Variation Characteristics of Annual Daytime Rainfall in Sichuan Province

摘要: 利用四川省126个气象站点1961~2021年共61年逐日降水观测数据，采用经验正交函数分解(Empirical Orthogonal Function Decomposition，以下简称EOF分解)、旋转经验正交函数分解(Rotated Empirical Orthogonal Functions Decomposition，以下简称REOF分解)等多种现代气候诊断分析方法，详细地研究了四川省年昼雨的时空分布特征。结果表明：1) 四川省年昼雨呈现典型的经向分布，自东向西依次递减，高值中心位于万源，昼雨达747.6 mm，低值中心位于川西高原的巴塘，昼雨仅为129.4 mm；年昼雨日数除川西高原的山前平原较多外，其余区域较为均匀，在峨眉山最高可达166.951天，在巴塘最低可达64.656天；年昼雨强度高值中心位于川东北万源和川西南山地的宁南，年昼雨强度分别为6.48 mm/h和7.271 mm/h，低值中心位于川西高原的石渠，年昼雨强度为1.91 mm/h；年昼雨趋势表现为川西高原和川东北丘陵地区逐步增加，高值中心位于大竹，趋势系数为0.415，而四川省中部和东南部逐渐减少，低值中心位于普格，趋势系数为−0.381，均通过信度0.05的显著性检验。2) 四川省年昼雨的EOF前5个模态表明：第1模态的年昼雨表现为“中间正，两头负”，高振幅中心位于德阳；第2模态的年昼雨表现表现为自东南向西北逐渐由正转负型，高振幅中心位于阆中；第3模态的年昼雨表现表现为北正南负型，高振幅中心位于都江堰；第4模态的年昼雨呈现为典型的经向分布；即自西向东逐渐由正转负，高振幅中心位于川西高原的炉霍；第5模态的年昼雨表现表现为正负值交错分布型，振幅中心位于川西南山地的会理。根据REOF结果可以将四川省年昼雨变化分为川东南、川东北、成都平原、川西高原和川南山地5个区域。

Abstract: Based on the daily precipitation observation data from 126 meteorological stations in Sichuan Province from 1961 to 2021, a total of 61 years, this study utilized multiple modern climate diagnostic analysis methods, including Empirical Orthogonal Function Decomposition (EOF decomposition), Rotated Empirical Orthogonal Functions Decomposition (REOF decomposition), to comprehensively investigate the spatiotemporal distribution of the annual daytime precipitation in Sichuan Province. The results show that: 1) The annual daytime rainfall in Sichuan Province shows a typical meridional distribution, decreasing from east to west. The high-value center is located in Wanyuan, with a daytime rainfall of 747.6 mm, while the low-value center is in Batang on the western plateau of Sichuan, with a daytime rainfall of only 129.4 mm. The annual number of daytime rainfall days is relatively uniform in most areas except for the piedmont plain of the western plateau, where it is relatively high. The highest number of days is 166.951 in Emeishan, and the lowest is 64.656 in Batang. The high-value centers of annual daytime rainfall intensity are located in Wanyuan in northeastern Sichuan and Ningnan in the mountainous area of southwestern Sichuan, with intensities of 6.48 mm/h and 7.271 mm/h respectively. The low-value center is in Shiqu on the western plateau of Sichuan, with an intensity of 1.91 mm/h. The trend of annual daytime rainfall shows an increasing trend in the western plateau and the hilly areas of northeastern Sichuan, with the high-value center in Dazhu and a trend coefficient of 0.415. Meanwhile, it shows a decreasing trend in the central and southeastern parts of Sichuan, with the low-value center in Puge and a trend coefficient of −0.381. All these trends have passed the significance test at the 0.05 confidence level. 2) The first five EOF modes of annual daytime rainfall in Sichuan Province show that: the first mode of annual daytime rainfall is characterized by “positive in the middle and negative at both ends”, with the high amplitude center located in Deyang; the second mode of annual daytime rainfall shows a gradually changing pattern from positive in the southeast to negative in the northwest, with the high amplitude center located in Langzhong; the third mode of annual daytime rainfall shows a pattern of positive in the north and negative in the south, with the high amplitude center located in Dujiangyan; the fourth mode of annual daytime rainfall presents a typical meridional distribution, that is, gradually changing from positive in the west to negative in the east, with the high amplitude center located in Luhuo on the Sichuan Western Plateau; the fifth mode of annual daytime rainfall shows an alternating distribution of positive and negative values, with the amplitude center located in Huili in the mountainous area of southwestern Sichuan. According to the REOF results, the annual daytime rainfall variation in Sichuan Province can be divided into five regions: southeastern Sichuan, northeastern Sichuan, Chengdu Plain, Sichuan Western Plateau and mountainous area of southern Sichuan.